FCC to review the relative value of low, high, and super-high spectrum licenses

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According to the Wall Street Journal, the FCC is reviewing the rules it has for spectrum license ownership, particularly on how much spectrum any one company can hold.

The FCC is considering reworking them because they do not currently account for the properties of different frequencies of spectrum. There are three main classes of spectrum for cellular wireless networks: low band, high band, and super high band. Each of these classes of spectrum have different properties that make them desirable in certain circumstances.

Low band spectrum is on frequencies below 1GHz (1000MHz). Cellular 850 (850MHz) and Digital Dividend (700MHz) spectrum are examples of low band spectrum. This spectrum is considered highly valuable because cellular wireless networks (like LTE) that operate on those frequencies can penetrate buildings better and require fewer towers to offer the same breadth of coverage. However, the trade-off is that these frequencies offer less capacity than higher band frequencies too. This is a consequence of using fewer towers to deploy the same breadth of coverage. For rural areas, this spectrum is ideal due to the inherent cost savings in using fewer towers to cover the area. Sprint, AT&T, and Verizon Wireless have some spectrum of this kind.

High band spectrum is on frequencies above 1GHz but are typically below 3GHz (3000MHz). AWS (1.7GHz/2.1GHz), PCS (1.9GHz), and IMT (2.1GHz) are examples of high band spectrum. With this type of spectrum, networks have high amounts of network capacity in exchange for characteristically weaker indoor network performance. This type of spectrum is much better if the network is supposed to support larger numbers of subscribers at once with decent performance levels. However, it is more expensive to deploy because the shorter ranges of the towers mean that more towers are required to offer a wide breadth of coverage. The indoor performance issues can be mitigated somewhat with these frequencies, so it is considered the “sweet spot” for population densities of urban areas. T-Mobile, Clearwire, and many regional operators exclusively use high band spectrum for their networks.

Super high band spectrum is on frequencies above 3GHz. These frequencies are not commonly used for cellular wireless networks, as they offer the extreme version of the characteristics of high band spectrum. Notably, this spectrum is extremely poor at indoor network performance. Line of sight becomes quite a bit more important at this level, as well. In order to receive the signal more reliably, transmitters and receivers are often within the human visible distance due to the weak propagation of radio waves at that level.

Obstructions are often minimized in order to improve radio performance, as well. However, networks deployed on these frequencies can handle a lot more at once, so these are often used for wireless backhaul (backbone connections to the internet) for networks. There are cellular wireless networks coming into existence that use these frequencies due to the lack of low band and high band spectrum, though. This is happening in Europe and Asia for now, but could spread to the Americas as well. But, deployment of networks on these frequencies is ridiculously expensive because many more towers need to be built to offer the same breadth of coverage that high band spectrum can offer. Of course, these networks would have a lot more capacity, so it is particularly suitable for large metropolitan areas.

The cellular wireless service industry places a higher value on low and high band spectrum over super high band spectrum because of the economics of covering populations with cellular wireless. Most areas are not large metropolitan areas, so a mix of low band and high band spectrum in most areas can cover a country quite well. In the United States, T-Mobile USA is the only carrier of the four national carriers working solely with high band spectrum. As a result, it has to deploy more to offer the same breadth of coverage that AT&T and Verizon can offer. Clearwire is in a similar boat, though it is transitioning from WiMAX to LTE-Advanced TDD before expanding anymore.

Sprint and AT&T both welcome the FCC’s review and potential adjustment of these rules, as they believe that the FCC does not fairly judge spectrum allocations based on these market realities. The FCC currently uses an unweighted spectrum screen, in which a chunk of low band spectrum is counted the same as a chunk of high band spectrum. Given that low band spectrum is valued favorably against high band and super high band spectrum in the market, it makes sense for the FCC to adjust its rules in order to more accurately determine how much spectrum any one company needs.

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Well, damn…that was a far better read than I anticipated. Very informative.

http://www.facebook.com/InklingBooks Michael W. Perry

The FCC also needs to think about how we can use spectrum more efficiently. Quite a bit of the data going through cellular channels, from sportscasts to news, could be broadcast by digital television stations. That’d get excellent coverage and used existing spectrum. Smartphones would just have to be made smart enough to store those broadcast for later use.

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